There is a growing consciousness of the need to conserve water, particularly in toilets where it is not always necessary to have a full flushing of the toilet. In order to conserve flushing water, attempts have been made at providing two step flushing control type systems wherein there are two flushing modes. One of the modes is a full discharge flushing and the other is a water saving or partial flushing mode.
Typical toilets include a flush handle mounted on the outside of the tank. When the handle is manually pressed a valve, such as a flapper valve, is lifted from the valve seat. The flapper valve includes an inverted air chamber so that it initially floats as it is lifted away from the valve seat or drain outlet. This floating flapper valve permits water to flow into the bowl even if the user immediately releases the flush handle. As the body of water flows through the drain outlet of the tank it starts the syphoning action in the bowl and flushes the standing water in the bowl along with its waste contents into the sewer line. When the tank is nearly empty the flapper valve closes and the tank continues to fill as the float ball connected to the ball cock rises. At the same time water from the ball cock valve enters an overflow tube to refill the bowl to its normal water level and the bowl cock valve closes.
Because of water shortages, particularly those which periodically result in significant portions of the United States, there have been major conservation efforts including efforts directed to conventional toilets which are wasteful and inefficient since a relatively large quantity of water is used to accomplish every flush.
Patents directed toward dual flush operations are U.S. Pat. Nos. 6,704,945, 5,943,708 and 5,375,268.